Preparation of titanium pigments



- Patented Jan. 7, 1936 UNITED STATES PATENT OFFICE 7 2,026,862PREPARATION or TITANIUM PIGMENTS No Drawing. Application May 15, 1930,Serial No. 452,810

12 Claims.

This invention relates to improvements in the preparation or manufactureof titanium pigments and the improved products resulting from suchimproved process.

Titanium pigments have been used extensively as substitutes for otherpigments and have shown a general superiority over such pigments,especially when compared to other white pigments. They are, however,inclined to become powdery or to chalk off and this characteristic makesthem objectionable for use where they will be exposed to the weather.

' This application is a continuation in part of our 'copendingapplications Serial Numbers 2,233 15 and 2,234, filed January 13, 1925.

It is an object of the present invention to provide a process forpreparing a titanium pigment of improved characteristics and one whichmay 0 be safely used where it will be exposed to the weather. It isanother object to provide a method for preparing a pigment havinggreater durabilityand one which will not be subject to the above defect.It is also an object of the invention to improve the quality of thepigment by controlling the conditions under which it is sintered.Another object of the invention is to produce a new pigment of improvedcharacteristics. Other objects will become apparent. so The invention,broadly stated, comprises adding to precipitated titanic acid,substances which will improve the characteristics of the pigmentresulting from the calcining .operation. It also includes the additionof substances adapted to fill and remain in the interstices or pores ofthe titanium pigments as well as the addition of materials adapted toassist in the sintering action but which materials may be subsequentlywashed from the pigment. In view of the pigmentary qualities required inthe finished product, the materials added to fill the interstices orpores should have the essential characteristics of pigments or at leastthey should not detrimentally affect the pigmentary qualities of theproduct. It is also desirable that the material used for this purposebe'one which may be applied to the titanium oxide by precipitation orcoagulation from the solution in which the latter is suspended and onewhich will with- 50 stand the calcination to which the composite pigmentis subjected. The filling or closing of the interstices or pores of thetitanium oxide by the deposition of the finely divided particlesresulting .from the coagulation or precipitation, and thev 55 retentionof these particles during the drying and 'Further, these oxides andhydroxides may or may calcining steps, result in a product havingincreased durability and decreased oil absorption.

and may be applied to the titanium oxide by precipitation or coagulationfrom solutions in which the titanium oxide is suspended.

We have also found that an improvement in 10 the sintering of the abovecomposite pigment or of the titanium oxide alone, may be accomplished byeffecting the sintering in an acid atmosphere produced by freeacids orby the heating of salts of an acid character. It is preferable to usefor 15 this purpose salts whose residues may be removed by washing thecalcined product. Magnesium chloride, ammonium sulphate, and alkalisalts are examples of substances suitable for this purpose.

In carrying out our improved process, the titanium oxide may be mixedwith the rare earth ,compound, preferably the hydroxide or oxide incolloidal solution, and the rare earth oxide or hydroxide may bedeposited upon, and within the 25 pores of, the particles of titaniumoxide either by precipitation or coagulation. The composite precipitateresulting from the filling of the pores of the titanium oxide with therare earth oxide or hydroxide may then be calcined at 800-1000 30 C. togive it the desired pigment properties.

Titanium oxide'adaptable to be pore filled as described herein may beobtained conveniently from the main titanium product of. the process Fdescribed in United States Patent 1,504,672, but tetravalent oxides oftitanium obtained by precipitation and having any degree of hydrationare also suitable and can be used in the present case.

not be dried and/or calcined before they are put in suspension in thesolution. In cases where the oxide has been calcined it is, of course,preferable to bring it first to a fairly fine state of division.

In order to describe our invention more clearly, the following specificexamples are given. It is not intended, however, to restrict theinvention to the particular conditions and proportions recited, since itis apparent that these examples are .only illustrative and manymodifications may be made to obtain the desired improvement.

I Example I About '1 to 10 parts by weight of finely ground, 5

preferably calcined, titanium oxide is suspended in 100 parts by weightof a solution of titanium or titanyl sulphate containing about 200 gramsI of titanium oxide per litre. This sulphate solution may be obtained bythe customary procedure of treating ilmenite with sulphuric acid. The

mixture is heated to hydrolytically precipitate Example II About 10parts by weight of calcined titanium 20 oxide are finely ground andmixed with 7 parts by weight of a colloidal thorium solution containingabout 300 grams of thorium oxide per litre of solution. The water of themixture is evaporated and calcination is effected at red heat.

25 The calcined product may be cooled and ground in a wet or drycondition.

The calcining of the titanium dioxide before depositing the thoriumoxide gives the particles 9. definite structure upon which the porefilling me.-

30 terlal may be deposited. It is apparent that a similar improvementmay be accomplished by adding the finely ground calcined titanium oxideto a colloidal solution of titanium oxide and coagulating the colloidaltitanium dioxide.

36 If preferred, the titanium or thorium oxide may be coagulated byheating and the water may be separated from the suspended material bydecanting and/or filtering, after which the composite solids may becalcined and ground.

40 An improved result may also be obtained by using moist precipitatedtitanium dioxide, containing about 50% water, in place of the calcinedmaterial referred to in the above illustrations.

a Sample III The pore-filled titanium oxide, referred to in the aboveexamples, may be calcined in the presence of a salt. For example, asmall quantity of colloidal titanium orthorium oxide may be 60 mixedwith titanium oxide and this mixture may be dispersed in sodium sulphatesolution. The sodium sulphate. will coagulate the colloidal titanium orthorium oxide and the water may then be evaporated or otherwiseseparated from 55 the mixture of solids which may then be calcined byheating to about 800-1000 C. After the calcining the sodium sulphateremaining upon the pigment may be separated by washing the .cal-

cined mixture. If desired, other salts, such as potassium carbonate, maybe substituted for the sodium sulphate.

- Example IV An improved product will also result from sin- 65 taxingthe titanium oxide with a salt, without the addition of a pore-fillingmaterial. As an iling acid may be removed by treating the moist or dryproduct with an oxide of a metal capable of reacting with the sulphate,for example, zinc oxide or magnesium oxide. A considerably smallerquantity of potassium bisulpliate, for example as little as 2% of theweight of titanium oxide, may be used.

Example V As another example of the heating of titanium 1,0 oxide withan alkali salt, 10 parts by weight of moist titanium hydroxide, obtainedfrom a neutral or basic titanium sulphate solution, are intimately mixedwith about 0.5 parts by weight of potassium carbonate, and the mixtureis heated for a suitable time, for example, two hours, at a temperatureof about 800-1000 C. The calcined material is washed first with water toremove the potassium sulphate and then with mineral acid untilcompletely neutral and is then dried. A considerably smaller quantity ofpotassium carbonate-may be used, for example, very satisfactory resultsare obtained by using potassium carbonate in the proportion of .5% ofthe titanium oxide.

If the oxide, referred to in the above examples, is obtained byprecipitating titanium sulphate solution, it will contain sumcientsulphuric acid to convert the alkali carbonate to a sulphate. A similarresult may be obtained by adding an alkali hydroxide.

The improvement in whiteness of the pigment resulting from the calciningin the presence of an alkali salt does not seem to be dependent upon thepresence of the sulphate radical, since similar improvement may beaccomplished by heating in the presence of other alkali salts.Improvements in results may be accomplished by adding the alkali salt inproportions up to about 2% of sodium salt, but the addition of a greateramount does not greatly improve the whiteness of the product. Thequantity of water soluble salt present during the calcining may beregulatedby controlling the concentration of the solution from which thesolids are separated or by washing the separated solids so as to removea portion only of the water soluble salt.

It is apparent that various modifications and combinations of the aboveillustration may be used and that the quantities may be varied and it isnot intended to restrict the invention to the particular embodimentdescribed. In the appended claims the term titanium-thorium family isused to include these elements, together with zirconium and cerium.

The sintered product produced according to the above processes, ormodifications of these processes, may be ground wet or dry and mixedwith the usual diluting agents and fillers, such as barium sulphate,zinc oxide and others, to produce a durable primary material for paintsand other covering materials and one which may be applied where it is tobe exposed to the weather.

What we claim is:

1. A process for the manufacture oi titanium pigments which comprisessuspending titanium dioxide particles in a solution of a thoriumcompound, and heating said solution and thereby hydrolyticallyprecipitating thorium dioxide on 70 said suspended particles.

2. A process for the manufacture of titanium pigments which comprisessuspending particles of titanium dioxide in a solution of a thoriumcompound, heating said solution and thereby hy- 76 v drolyticallyprecipitating thorium dioxide on said suspended particles, separatingsaid mixture from solution, freeing said mixture from acid, andcalcining the same. I 3. In a process for the production of a titaniumpigment the steps of suspending particles of titanium dioxide in asolution of a compound of one of the elements selected from the group ofelements consisting of cerium, thorium and zirconium, and treating saidsuspension to precipitate an oxide of one of said elements in thepresence of said titanium dioxide.

4. A calcined composition for use as a pigment comprising titaniumdioxide having an oxide ofone of the elements selected from the group ofelements consisting of cerium, thorium and zirconium within its pores.

5. In a process for the production of a titanium pigment the steps ofsuspending particles of titanium dioxide in a solution of a ceriumcompound and treating said suspension to precipitate a cerium oxide inthe presence of said titanium dioxide.

6. A calcined composition for use as a pigment comprising titaniumdioxide having cerium oxide within its pores.

7. In a process for the production of a titanium pigment the steps ofsuspending titanium dioxide in a) solution of a zirconium compound andtreating said suspension to precipitate a zirconium oxide in thepresence of said titanium dioxide.

8. A calcined composition for use as a pigment comprising titaniumdioxide having zirconium oxide in its pores.

9. A calcined composition for use as a pigment comprising titaniumdioxide having thorium oxide within its pores.

10. In a process for the production of a titanium pigment the steps ofsuspending particles of titanium dioxide in a solution of a compound ofone of the elements cerium, thorium and zirconium, treating saidsuspension to precipitate an oxide of one of said elements in thepresence of said titanium dioxide and calcining said mixture.

11. In a process for the production of a titanium pigment the steps ofsuspending particles of titanium dioxide in a solution of a ceriumcompound, treating said suspension to precipitate an oxide of cerium inthe presence of said titanium dioxide and calcining said mixture.

12. In a process for the production of a titanium pigment the steps ofsuspending particles of titanium dioxide in a solution of a zirconiumcompound, treating said suspension to precipitate a zirconium oxide inthe presence of said titanium dioxide and calcining said mixture.

JOSEPH BLU'MENFELiD. MAX MAYER.

